I just changed my O2 sensor in my 91? olds calais 2.3 quad 4 and it starts fine and then after a short ride when i put in the park (or neutral) the engine revs high. But when i put it in neutral and let it roll to approx. 5 mph the reving goes back to normal but when i stop it revs high again. Any help is appriciated. Thanks in advance.